I don't see the point of the study tbh. ~~But neither the outrage~~. Mostly because not every country vaccinates at the same time after birth so there's no need to test it specifically. Just compare infants from different countries.
You don't even have to go that far. Denmark vaccinates right after birth (if I can understand Der gives tre doser på hhv. dag 0, efter 1 måned og efter 6 måneder. correctly) while Germany vaccinates after 2 months: Die ersten beiden Impfungen im Alter von 2 und 4 Monaten, die dritte Impfung im Alter von 11 Monaten. Literally just take a sample from both of these countries.
I was apparently vaccinated after 2 months, 3 months, 4 months and 1 year according to my vaccine certificate.
Edit: Small update, can see the issue with doing this in Guinea-Bisset

That makes more sense, I somehow skipped the sentence (in the image) mentioning the high rate.
I was a bit mislead by the claim this study couldn't be done in the US/Denmark because of medical ethics. More like it would have been unethical and not approved were the infection rate equally as high. If the point is only seeing whether there are neurodevelopmental disabilities associated with administering the vaccine right after birth then obviously Guinea-Bisset would be the very last choice.
Thanks for pointing this out though!